1. Field of the Invention
One inventive aspect relates to a write-once optical information recording medium and an apparatus used for manufacturing the same. Specifically, the inventive aspect relates to an optical information recording medium suitable for recording with laser light at a wavelength of approximately 360 to 450 nm (so-called blue laser light) using a semiconductor laser and to a mold apparatus used for manufacturing the same.
2. Description of the Related Technology
Write-once optical information recording media using blue laser light at a shorter wavelength of about 360 to 450 nm, e.g., blue laser light at 405 nm, are currently being developed. The optical information recording media each include a recording layer using an organic dye compound so that the organic dye compound is decomposed or deteriorated by absorption of laser light to obtain, as a degree of modulation, a change in optical properties of the laser light at a recording/reproduction wavelength, for performing recording and reproduction.
For example, as disclosed in Japanese Unexamined Patent Application Publication No. 2005-302272, the optical information recording media each include a reflective layer, a recording layer, and a protective layer which are formed on a substrate, a spiral groove referred to as a “groove” being formed in a portion (recording area) of the substrate in which the recording layer is to be formed. In recording data on such optical information recording media, pits are formed in the grooves. The recording area is divided into a preformat area in which recording condition data such as media ID and laser power is previously stored, and a data area in which information is recorded by a user. The two areas have different groove spacings (track pitch), and the track pitch in the preformat area is wider than that in the data area.
Among these optical information recording media, a Low-to-High system optical information recording medium has the tendency that a push-pull (NPPb) signal is increased. In particular, in the preformat area having a wider track pitch, the NPPb signal is further increased, thereby causing the problem of failing to effect tracking.